Method of preventing adhesion of pitch to cooling slab



Feb. 14, 1967 s. GOBLA ET Al. 3,304,252

METHOD OF PREVENTING ADHESION OF' FITCH TO COOLING SLAB Filed Nov. 13, 1965 2 Sheets-Sheet l :E1-E1: 1 51"' L j; Il

2 /NVE/vroRs STEPHEN GOBLA and WILL/.4M 7 TAT By WM/6% Feb; 14, 1967 S. GOBLA ET AL METHOD OF PREVENTING ADHESION OF FITCH TO COOLING SLAB STEPHEN GOBLA and WILL/AM I ATE Bf M2? I A Harney United States Patent O 3,304,252 METHOD F PREVENTING ADHESION 0F PITCH T0 COOLING SLAB Stephen Gobla and William T. Tate, Gary, Ind., assignors to United States Steel Corporation, a corporation of Delaware Filed Nov. 13, 1963, Ser. No. 323,479 2 Claims. (Cl. 208-39) This invention relates to av method of disposing of molten pitch and, in particular, to a method for preventing adhesion of hot pitch to a cooling slab, thus facilitating the removal of the pitch when solid, with a minimum of dust.

Coal-tar pitch is a by-product of conventional cokeplant practice. Ordinarily, molten pitch is pumped to a large cooling bay. This area usually comprises a concrete or steel pad or slab having a steel retaining wall disposed theretround with a removable gate or section therein for access by mobile loading equipment. After air cooling about 24 hours, the pitch is broken into lumps with digging equipment and loaded into a car for shipment.

Among the disadvantages of this practice is the fact that the pitch adheres so tightly to the slab that considerable fines and dust are created by the required digging operation. The dust adheres to the lumps and tends to agglomerate them, especially during summer weather. This necessitates digging to unload a car at its destination.

We have discovered a greatly improved method of disposing of molten pitch. ln accordance with our invention, we maintain a layer of cooling liquid on the slab, before pouring molten pitch thereon. We then spray the liquid onto the pitch while it is being poured, until substantially all the slab area is covered. The coolingliquid layer is maintained at a small depth to form and to maintain an undulating pitch surface adjacent the slab area. Pitch that exhibits this undulating surface does not adhere to the slab and may be lifted easily therefrom. Continued spraying until the mass is solidified develops cracks therein. This facilitates fracture of the mass into lumps with a minimum of dust. The admission of cooling liquid is regulated to effect these results and to provide an excess which drains from the cooling bay.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawings illustrating the present preferred practice. ln the drawings:

FIGURE 1 is a plan view of a pitch-cooling bay and auxiliary equipment for carrying out the method of our invention;

FIGURE 2 is a vertical section taken on a line II-II of FIGURE l;

FIGURE 3 is a front elevation showing the access gate to the bay taken on a line IIl-lll of FIGURE 1; and

FIGURE 4 is a vertical section taken on a line IV-IV of FIGURE 3.

Referring now in detail to the drawings, a typical pitch-cooling bay comprises a concrete slab 2 having disposed therearound beams 4, held in place on the slab by anchor bolts 6. The structure includes spaced, vertical beams 8 disposed on the web of beams 4 and welded thereto. The inner, vertical periphery of the structure is defined by the inner flanges of beams 4, plates 10 supported thereon and attached to beams 8, and angles 12 longitudinally disposed on an-d attached to beams 8 and plates 10. An opening 14 in the structure and a ramp 16 leading thereto permit mobile equipment to enter the bay and remove the pitch. During molten pitch flow, opening 14 is closed by a gate 18. Gate 18 .comprises ice a channel 20, suporting plates 22, 24, stilener plates 26 and brackets 28 for attaching hooks and cables to move the gate. Spaced studs 30 welded to beams 4 pass through slots 32 in gate 18. When the gate is positioned, nuts 34 may be applied to bolts 30 to secure the gate. The inner periphery of the pitch bay structure is appreciably higher than the gate to permit mobile loading equipment to push and pile pitch lumps against the structure in a loading operation.

A fire hydrant 36, equipped with a hose 38 and a conventional fire fog nozzle 40, provides the required c001- ing and spray water. Molten pitch is pumped from a source (not shown) through a pipe 42 and may be introduced to the bay at spaced-apart points Iby pipes 44, 46 controlle-d by valves 48, 50 and 52.

After gate 18 is set in plate, the bay is flooded with water from hydrant 36 and the flow regulated to establish and to maintain a preferred layer. The pitch bay is not water tight. vWater may seep between slab 2 and beams 4 until pitch seals these openings. However, water can always drain at the four corners through openings 54 between the beams 4. Water supply is adequate for the complete operation plus this leakage.

Valves 48 and 50 are opened and molten pitch at a temperature between about 180 and 250 C. is pumped through pipes 42, 44 to the bay. The softening point of the pitch may vary between about and 150 C. The pitch thus spreads progressively and in an arc of increasing diameter over the slab to beams 4, pushing water ahead of it. The initial, advancing pitch layer is cooled and solidified by its contact with water. This pitch layer approximates the depth of water. Immediately behind the initial layer and superimposed thereon, a second layer of fresh molten pitch advances, continually extending the area covered.

As the molten pitch is poured into the bay, the nozzle 40 is elevated and a spray of water is permitted to fall gently on the advancing pitch layer. This practice avoids turbulence and penetration of the pitch which would cause deleterious water inclusion. Depending on such factors as the pitch temperature and softening point, the spray may be continuous or intermittent. The volume of spray water is controlled to maintain the depth of the water layer on the slab between about one-half and one inch.

As the water layer is decreased below about one-half inch, the advancing pitch layer is progressively decreased in thickness and the cooling slab is covered more quickly. The sensible heat in the fresh molten pitch, however, will eventually ca-use a thinner solidified layer to melt and the surface thereof adjacent the slab to adhere thereto. As the depth of the water layer is increased above about one inch, the advancing pitch layer is progressively increased in thickness. A thicker pitch layer, however, will eventually and suddenly build up in thickness beyond the thickness of the water layer to between 6" and 10 and halt further progressive flow o-f the pitch. The exact depth limits of the water layer at which the described diffculties will occur depend on such factors as the temperature and softening point of the pitch.

With decreasing temperature, the pitch becomes progressively more viscous and reduces the upper limit of maximum thickness. With decreasing softening point, less heat is required to melt the pitch and thus reduces the lower limit o-f minimum thickness. F-or normal coke-plant operation, the described one-half to one inch cooling water layer has been found generally satisfactory and will allow for some variation in the level of the cooling slab. The above explanation, however, will permit practice of the invention when the pitch properties vary, -for example,

when handling wood pitch, asphalt pitch, petroleum pitch or the like.

The described water spraying is continued after the slab is covered with pitch and until the required quantity has been pumped into the bay. We have found that the described operation effectively prevents adhesion of pitch to a slab. Surprisingly, the surface of pitch adjacent the slab is shiny and exhibits an undulating pattern. The main Waves, radiating from the molten pitch source, exhibit a number of ap preciably smaller ripples therebetween.

The described water spraying may be terminated shortly after the flow of molten pitch has ceased. The described undulating pattern permits loading equipment to lift the pitch easily from the cooling slab in large pieces. However, important benefits result from continuing the Water spraying until .the mass has solidified. This rapid cooling tends to develop radial cracks or fractures in the mass, some visible, some invisible. The cooling time is decreased. M-ore importantly, however, the pitch now fractures into manageable lumps and with a minimum formation of dust and fines. The invention has reduced production of lines to between about 3% and 5% from the conventional 20%.

A specific example of the practice of the invention, giving quantities involved, is set forth below.

A pitch-cooling bay measuring about 71 X 71 having a concrete slab was flooded with water to a depth between about one-half and one inch. A hydrant 36 having a capacity of about 150 gallons per minute easily maintained this layer.

Thereafter, valves 48 and 50 were gradually opened and molten pitch pumped through pipes 42 and 44. After a few minutes, the maximum pitch flow of about 200 gallons per minute was developed and continued until the lrequired 12,000 gallons had been poured in the bay, to an average depth of about 4". The depth may be varied depending on pitch requirements.

The coal-tar pitch had a temperature of about 220 C. and a softening point of about 110 C., cube in air. After maximum pitch flow had developed, nozzle 40 was tilted upwardly and a water spray rained on the flowing pitch for about 2 minutes, at intervals of about 5 minutes, during flow of pitch. When pouring ceased, the water spray was operated continuously between about 4 and 8 hours, the pitch mass gradually soldifying from the perimeter to the center of the bay. Radial cracks and fractures then developed in the mass. Thereafter, gate 18 was removed, mobile equipment broke up the pitch into lumps with ease and loaded them for shipment. The fines averaged between about 3% and 5%. The surface of the lumps adjacent the slab exhibited the described undulating pattern. The pitch had a water content of about 0.1%

While lthe above example illustrates a preferred method of operation, other conditions of operation may be used without departing from the spirit of the invention. Depending on such factors as pitch temperature and softening point, the pouring of pitch may be alternated between pipes 44 and 46 to prevent adhesion of pitch to the bay. Thus, for example, with high pitch temperature and a low softening point, the total heat to be removed becomes appreciably greater. After pouring for an interval from one source, that area may be cooled while pitch is poured from a spaced-apart source. The second area is cooled frm the same or another source of cooling liquid. While water is the usual cooling liquid, other available liquids may be used that are not deleterious to the pitch. The temperature of the pitch may vary widely depending on the final distillation temperature and also upon the softening point which may vary between about 40 C. and 190 C. Where sufficient cooling liquid is available, a bay that is not water tight is preferred, since the liquid layers and requirements may be easily provided by the usual controls, while `assuring a continuous flow of cooling liquid. The invention may be practiced with a water-tight bay, however, since much water is evaporated. The rate of water flow need only be regulated to balance evaporation loss. Additionally, the initial water layer can -be set at a minimum and then allowed to buildup to a maximum as the bay is covered with pitch.

The invention is characterized by several distinct advantages. In the first place, our procedure for preventing pitch from adhering to a cooling slab is relatively simple, inexpensive and effective. It permits handling of pitch more economically and with appreciably less dust than in the conventional process.

Secondly, the process can be easily varied to handle coal-tar pitches in relatively wide temperature and softening-point ranges. Utilizing the principles of this inven tion, other pitches with properties o-utside these limits may be processed.

Finally, the process appreciably reduces the time required to cool a bay of pitch over conventional methods.

Although we have disclosed herein the preferred practice of our invention, we intend to cover as well any change or modification therein which may be made without departing from the spirit and scope of the invention.

We claim:

1. A method of solidifying molten pitch which comprises providing a layer of cooling water on a slab to a predetermined depth or at least about one-half inch, then pouring molten pitch onto said slab to provide a layer of solidified pitch having a depth approximating the depth of said water laye-r, then pouring additional molten pitch onto said solidified pitch layer, the thickness of said soliditied pitch layer being such that the additional molten pitch will not remelt it to said slab, and cooling the additional molten pitch to solidify the same.

- 2. A method as defined in claim 1 wherein vadditional molten pitch is poured on top of the solidified pitch until the required quantity thereof has accumulated, spraying Water on the additional molten pitch to cool and to solidify the same land thereafter continuing said water spraying until cracks are formed in the solidified patch.

References Cited by the Examiner UNITED STATES PATENTS 1,088,635 2/1914 Stevens 208-39 FOREIGN PATENTS 740,05 5 10/ 1943 Germany. 743,678 5 1943 Germany.

DANIEL E. WYMAN, Primary Examiner.

PATRICK P. GARVIN, P. KoNoPKA,

' www Examiners, 

1. A METHOD OF SOLIDIFYING MOLTEN PITCH WHICH COMPRISES PROVIDING A LAYER OF COOLING WATER ON A SLAB TO A PREDETERMINED DEPTH OR AT LEAST ABOUT ONE-HALF INCH, THEN POURING MOLTEN PITCH ONTO SAID SLAB TO PROVIDE A LAYER OF SOLIDIFIED PITCH HAVING A DEPTH APPROXIMATING THE DEPTH OF SAID WATER LAYER, THEN POURING ADDITIONAL MOLTEN PITCH ONTO SAID SOLIDIFIED PITCH LAYER, THE THICKNESS OF SAID SOLIDITIED PITCH LAYER BEING SUCH THAT THE ADDITIONAL MOLTEN PITCH WILL NOT REMELT IT TO SAID SLAB, AND COOLING THE ADDITIONAL MOLTEN PITCH TO SOLIDIFY THE SAME. 